1. Field of the Invention
The present invention relates to an aircraft actuator hydraulic system that includes hydraulically operated actuators for driving a control surface of an aircraft and that supplies pressure oil to the actuators.
2. Description of Related Art
An aircraft is provided with control surfaces that are formed as moving surfaces (flight control surfaces) and are configured as an aileron, an elevator, a rudder, and the like. Hydraulically operated actuators are often used as actuators for driving such control surfaces. Note that, as disclosed in JP 2003-040199A, in an aircraft, for example, two hydraulically operated actuators are attached to one control surface and the control surface is driven by these two actuators.
Pressure oil is supplied to an actuator such as the above from an aircraft central hydraulic power source. Also, pressure oil is supplied to two actuators from separate aircraft central hydraulic power sources serving as separate systems. Accordingly, even if a loss or degradation in the function (pressure oil supply function) of one of the aircraft central hydraulic power sources occurs, it is possible to drive the control surface by one of the two actuators, thus ensuring high reliability.
The hydraulic system disclosed in JP 2007-046790A is known as a hydraulic system (aircraft actuator hydraulic system) that can ensure even higher reliability at the occurrence of a loss or degradation in the function of an aircraft central hydraulic power source. The hydraulic system disclosed in JP 2007-046790A includes a pump provided independently of the aircraft central hydraulic power sources, and is configured as a hydraulic system capable of supplying pressure oil to actuators when a loss or degradation in the function of an aircraft central hydraulic power source occurs. The pump of this hydraulic system is provided so as to be able to raise the pressure of the pressure oil discharged from the actuators and supply the pressure oil to the actuators. Also, this pump is configured to be operated when an aircraft central hydraulic power source undergoes a loss or degradation in its function due to a pressure decrease.
As described above, for an aircraft, it is necessary that a control surface can be driven by any of a plurality of actuators in order to ensure reliability at the occurrence of a loss or degradation in the function of an aircraft central hydraulic power source. For this reason, being able to secure an output that allows each actuator to drive a control surface on its own is a major factor in determining the size of the structure of the actuators. Therefore, there are severe constraints on reducing the size of the actuators.
Meanwhile, recently, there is a demand for coping with thinned wings, i.e., the reduction of the wing thickness, for the purpose of improving the efficiency of the aircraft body to increase the fuel efficiency, and, in the case where an actuator is installed inside a thinned wing, it is very important to reduce the size of the actuator. Note that, in the case where the actuator cannot be reduced in size and thus cannot be installed inside a thinned wing, the actuator will be installed on the outside of the wing. In this case, even if a fairing for covering the surface of the actuator is provided for reducing the aerodynamic drag, it is difficult to sufficiently reduce the aerodynamic drag, resulting in a reduced efficiency of the aircraft body.
As the method for reducing the size of a high-output actuator so as to allow the actuator to be installed inside a thinned wing, it is conceivable to adapt the aircraft central hydraulic power sources to high pressure. This allows for a high output for an actuator even if it has a small pressure receiving area, and therefore the size of the actuator can be reduced. In this case, however, it is necessary to adapt the entire hydraulic system, from the aircraft central hydraulic power sources to the actuators, to high pressure. This leads to a significant cost increase due to, for example, the fact that a special material that can be adapted to high pressure needs to be used for the entire hydraulic system.